This invention relates generally to active carbon and the like and reactivation or revivification thereof and more particularly to an activation and revivification (hereinafter referred to as reactivation) apparatus which is highly suitable for the reactivation of active carbon.
Heretofore, reactivation of active carbon has been generally carried out by causing the carbon to undergo planar movement of a cascade movement through a hot space or over a hot surface heated by the combustion of a heat source such a fuel oil, gas fuel, or kerosene (paraffin oil) and, during this carbon movement, subjecting it to drying, firing, and steam injection.
By this known process, however, parts of the apparatus therefor must be made heat resistant to continually withstand high temperatures of the order of 90.degree. to 950.degree. C., but it is difficult to prolong the heat resisting life of the entire apparatus. For this purpose, large quantities of high-priced materials must be used, whereby the apparatus construction cost rises, and, moreover, a separate fuel combustion device becomes necessary. Furthermore, a large quantity of fuel becomes necessary. All of these problems combine to elevate the operational cost.
Still another difficulty is that a large space is required for carrying out the process steps of drying, firing, and reactivation, and the entire apparatus becomes considerably bulky and expensive. Moreover, a great quantity of active carbon must be processed in order to fully utilized this apparatus, and this gives rise to the generation of a large quantity of harmful gases leading to a pollution problem. Equipment for preventing the discharging of these exhaust gases or for processing these gases further increases the complexity and bulk of the apparatus. The ultimate result is that the fuel cost, labor cost, transportation, etc., are tremendously increased and have a great effect on the cost of operation, whereby the price of the active carbon thus reactivated approaches that of newly produced active carbon.
One solution which would appear to be possible for the above described problems of the prior-art reactivation apparatus comprises abandoning the use of conventional fuel as a heat source and causing the active carbon to pass between electrodes thereby to cause an electrical conduction and discharge effect, the joule heat thus generated being utilized to accomplish reactivation.
One specific form of apparatus which would appear to be suitable for solution comprises, essentially, a cylindrical drum structure and several anodes and cathodes installed alternately on the inner wall surface of the drum structure in the axial direction thereof, the drum structure being adapted to rotate about its axis, which is inclined, and to receive at its upper end active carbon to be reactivated. Then, when this drum structure is rotated, the active carbon flows downward as it contacts alternately the anodes and cathodes. During this process, according to design, the carbon is resistance heated by the electrical conduction and discharging action which occurs while it moves in interposed state between the anodes and cathodes and is thereby reactivated.
In this apparatus, however, the active carbon tends to move intermittently as groups of particles between the electrodes when the drum structure is rotated, whereby the agitation is insufficient, and, furthermore, there are instances in which the active carbon is not in a state of continual contact with the anodes and cathodes. In such instances, the electrical conduction and discharge action is not accomplished smoothly, and cases wherein the active carbon reaches the outlet of the apparatus without even being dried readily occur. Another problem is the difficulty of selecting the proper angle of inclination of the axis of the drum structure.